Résumé

Most conifer seeds die as seeds or seedlings within 5 years afterdispersal. Understanding what factors keep a few of them alive isessential if natural regeneration is to be maintained in managedforests. For example, decaying logs and the conifer seedlings thatoften grow on them are rare under certain canopies such as deciduoustrembling aspen (Populus tremuloides Michx.). We conducted a seedingexperiment to evaluate the role of certain substrates, and titterfall,on early conifer survivorship. Seeds of balsam fir (Abies balsamea(L.) Mill.), white spruce (Picea glauca (Moench) Voss), and easternwhite-cedar (Thuja occidentalis L.) were sown during 2 consecutiveyears on mineral soil, relocated logs, and litter in deciduous aspenand coniferous (Thuja occidentalis dominated) stands. Seedling survivorshipwas monitored at the end of the first growing season and 1 yearafter each sowing. Conifer seedling survivorship was equivalentor greater under aspen than under cedar-dominated canopies. Piceaand Thuja survivorship was highest on decaying logs of approximately9 cm high (compared with logs buried at forest floor level) andlowest on forest floor litter during both the first growing seasonand the following autumn-winter. Abies survivorship was little affectedby substrate type, except for low autumn-winter survival on litter.Thuja autumn-winter survival was significantly reduced by litterfallin both deciduous and coniferous stands.